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  <title>返回 log(1 + number)，甚至当 number 的值接近零也能计算出准确结果</title>

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</div><hr /><div id="function.log1p" class="refentry">
   <div class="refnamediv">
    <h1 class="refname">log1p</h1>
    <p class="verinfo">(PHP 4 &gt;= 4.1.0, PHP 5)</p><p class="refpurpose"><span class="refname">log1p</span> &mdash; <span class="dc-title">
     返回 log(1 + number)，甚至当 number 的值接近零也能计算出准确结果
    </span></p>

   </div>
 <div class="refsect1 description" id="refsect1-function.log1p-description">
  <h3 class="title">说明</h3>
     <div class="methodsynopsis dc-description">
      <span class="type">float</span> <span class="methodname"><strong>log1p</strong></span>
       ( <span class="methodparam"><span class="type">float</span> <code class="parameter">$number</code></span>
      )</div>

    <p class="para rdfs-comment">
     <span class="function"><strong>log1p()</strong></span> 返回 log(1 + <em><code class="parameter">number</code></em>)，甚至当
     <em><code class="parameter">number</code></em> 的值接近零也能计算出准确结果。
     <span class="function"><a href="function.log.html" class="function">log()</a></span> might only return log(1) in this case
   due to lack of precision.
    </p>
   </div>

 <div class="refsect1 parameters" id="refsect1-function.log1p-parameters">
  <h3 class="title">参数</h3>
  <p class="para">
   <dl>

    
     <dt>
<em><code class="parameter">number</code></em></dt>

     <dd>

      <p class="para">
       要处理的参数
      </p>
     </dd>

    
   </dl>

  </p>
 </div>

 <div class="refsect1 returnvalues" id="refsect1-function.log1p-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   log(1 + <em><code class="parameter">number</code></em>)
  </p>
 </div>

 <div class="refsect1 changelog" id="refsect1-function.log1p-changelog">
  <h3 class="title">更新日志</h3>
  <p class="para">
   <table class="doctable informaltable">
    
     <thead>
      <tr>
       <th>版本</th>
       <th>说明</th>
      </tr>

     </thead>

     <tbody class="tbody">
      <tr>
       <td>5.3.0</td>
       <td>
         此函数在所有平台上均可用
       </td>
      </tr>

     </tbody>
    
   </table>

  </p>
 </div>

 <div class="refsect1 seealso" id="refsect1-function.log1p-seealso">
  <h3 class="title">参见</h3>
  <p class="para">
   <ul class="simplelist">
    <li class="member"><span class="function"><a href="function.expm1.html" class="function" rel="rdfs-seeAlso">expm1()</a> - 返回 exp(number) - 1，甚至当 number 的值接近零也能计算出准确结果</span></li>
    <li class="member"><span class="function"><a href="function.log.html" class="function" rel="rdfs-seeAlso">log()</a> - 自然对数</span></li>
    <li class="member"><span class="function"><a href="function.log10.html" class="function" rel="rdfs-seeAlso">log10()</a> - 以 10 为底的对数</span></li>
   </ul>
  </p>
 </div>

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